1. Technical Field
The invention relates generally to axle suspensions for wheeled vehicles. More particularly, the invention relates to lift axle suspension systems for add-on axles. Specifically, the invention relates to lift axle suspension systems utilizing diaphragm chambers for selectively raising the wheels of a vehicle out of engagement with the road surface.
2. Background Information
Following World War II was the advent of large load-carrying capacity vehicles such as trucks and trailers. In the decades that followed, these vehicles rapidly ascended in popularity. Additionally, over the past decade or so, there has been a dramatic increase in the sale of pickup style trucks and sport utility vehicles resulting in a much broader range of people having vehicles with the capacity to pull light and medium duty trailers. With the advent and the continued demand for these large load carrying capacity trucks and trailers, and with the newer demand for light and medium duty trailers, came the need to provide add-on axles, for increasing the capacity of trucks and/or trailers which were manufactured with a limited number of axles.
While add-on axles effectively increased carrying capacity, it was soon realized that as the number of load bearing axles increased on a given vehicle, a number of difficulties arose. Specifically, tire scuffing, loss in fuel economy and the inability to safely corner, all were problems associated with add-on type axles. Mitigation of these problems was of primary concern to the industry, which concern resulted in the development of the lift axle suspension system. Such a suspension system could be selectively raised from the road surface or lowered into engagement with the road surface when needed, thereby mitigating the aforementioned problems.
Many types and varieties of lift axle suspensions or similar suspension systems have been designed and employed since their inception with varying degrees of success or failure. Two commonly used and industry accepted styles are the leading and trailing beam type and the parallelogram type, any of which may utilize either mechanical springs, torsion tubes, air springs and or a combination of these.
Among the most successful are those of the parallelogram air-powered lift type produced for example by Rockwell International. Another type is the upwardly biased leaf spring produced by Turner Quick-Lift Corporation of Canton, Ohio, such as disclosed in U.S. Pat. No. 3,185,621. Both of these types of units have the advantage of being safe, durable, effective for their intended purpose, useful in both the pusher (forward of the drive axle), and tag (rearward of the drive axle) positions and on both truck chassis and trailers alike.
While these and many other types of lift axle suspensions have operated effectively and solved an important need in the art, each of the designs is different resulting in a multitude of different design configurations, parts, methods of operation, functionality variations, etc. These known designs generally incorporate the use of leaf springs, other biased springs, or air springs or the like such as air bladders, air or lift bellows or other similar pressurizable devices, all of which have a number of drawbacks. Specifically, air springs are often complicated, expensive, difficult to use, difficult to maintain, bulky, and of many varying designs. Leaf springs or other biasable springs have other well known drawbacks. As a result, a failure or malfunction of a lift axle suspension in the field may result in significant downtime for the vehicle based upon a number of factors including: the need for a trained mechanic for that particular lift axle style or at least the air spring style that is thereon, and the need for repair or replacement parts that must often be ordered due to the specific nature of the parts to a specific air spring design. Both of these issues tend to make a repair, even one of a simple nature, a time consuming, and sometimes labor intensive and costly event.
Therefore, the need exists for a lift axle suspension system wherein standard, interchangeable, cost effective, readily available parts are integrated therein, and that most if not all mechanics in the truck maintenance field are capable and qualified to perform maintenance and repair thereon. Moreover, a need exists for such a lift axle suspension system where the new design simplifies or at least does not further complicate the overall suspension design. Still further, the need exists for such a lift axle suspension system which incorporates existing vehicle parts used on other systems on the vehicle, and thus readily understood, available, and interchangeable.
Objectives of the invention include providing an improved lift axle suspension system.
A further objective includes providing an improved lift axle suspension system in which the suspension system utilizes diaphragm chambers as part of the extensible and retractable lift mechanism in lieu of air springs or the like.
Another objective of the invention is to provide such a lift axle suspension system in which the suspension system utilizes diaphragm chambers embodied as brake chambers as part of the extensible and retractable lift mechanism in lieu of air springs or the like.
A further objective of the invention is to provide such a lift axle suspension system which is of simple construction, which achieves the stated objectives in a simple, effective and inexpensive manner, and which solves problems and satisfies needs existing in the art.
These and other objectives and advantages of the invention are obtained by the improved lift axle suspension system for selectively raising and lowering a vehicle or vehicle trailer""s tires into and out of engagement with a road surface, the general nature of which may be stated as including a mounting bracket rigidly affixed to a longitudinally extending frame member on the vehicle, a first and a second articulating arm each having first and second ends, the first end of each articulating arm being pivotally attached to the mounting bracket, and the second end of each articulating arm being pivotally attached to the axle, and at least one diaphragm chamber having a movable wall therein dividing the diaphragm chamber into an upper chamber and a lower chamber, and a push rod extending therefrom and translatable when the movable wall is moved whereby the push rod is interconnected to the lift axle suspension system in a manner such that translation of the push rod causes pivotal movement of the articulating arms and axle attached thereto.